Elastic fluid power plant



y 1945- F. NETTEL ET AL 7 2,379,452

ELASTIC FLUID POWER PLANT Filed Dec. 9, 1942 2 Sheets-Sheet 1 E/Ecfr/c Gen erafor so Fig.1.

2 Fan PU/ver Ike d Coat.

l/Exhauslz I N V EN TORS:

July 3, 1945. F. NETTEL ET AL 2,379,452

ELASTIC FLUID POWER PLANT Filed Dec. 9, 1942 2 Sheets-Sheet 2 IN V EN TORS' Patented July 3, 1945 UNITED STATES Emsrw FLUID rowan PLANT Frederick Nettel, Manhasset, andJolm Kreitner,

New York, N. Y. Y

' Application December 9, 1942, Serial No. 468,380

6 Claims.

The present invention relates to elastic fluid power plants, more especially to such including'a plurality of gas turbines arranged in parallel as regards the flow oi the fluid through them, a

source of compressed gas for the turbines and heating means for indirect heating of said compressed gas through heat transfer.

In plants'with' a usefulpower turbine and a compressor driving turbine arranged'in parallel,

'partialload operation predicates changes in the quantities of working air or ga fedto' the respective turbines; this is done in.known plants by flow regulating means immediately .in-i'ron't of the'inlets to the turbines. Such means are exp sed tothe highest temperaturesprevailing' in the systemsandthereiore expensive to build and I to maintain.

Itis an object of this invention to avoid this disadvantage.

It is anotherobject toutilize efiiciently the working fluid at a point before it enters the heating'means, i

(b) Keeping thetwo branch streams separate preheating and fuel burning heating means to the inlets of the two turbines arranged in parallel,

(c) Providing means for controlling the flow resistance in one or both of said branch streams, these means being arranged in front of all heating means, I

(d) Burning fuel for producing a heating gas stream passing through the high temperature side of the heating means,

(e) Leading expanded working fluid discharged irom one or both said turbines into said heating gas stream where the temperatureof said stream is substantially equal to or lower than the temperature of. the ex anded fluid at the point of its entrance to the'heater,

(f) Withdrawing a branch stream from said heating stream, where it has been cooled by heat transfer to a temperaturesuitable for the type of fuel burning means employed, and using the free, oxygen of this branch stream for the combustion of the tuel,

(g) Bifurcating the streamof combustion gases issuing from the combustion chamber in two branch streams, leading them separatedly through the heater, and providing meansi'or controlling the flow resistance in one or both of said branch streams; these means being arranged beis hindall heating means, i

(h) Controlling simultaneously the flow of the two branch streams of compressed working fluid,.

and the flow oi the two branch streams of combustion gases'in heat transfer relationship to the first said streams, V

(i) Controllingjointly the flow of one branch stream of compressed working fluid and the flow of the branch gas stream in heat transfer relationship thereto indefinite relationship to the heating end temperature-oi the compressed working fluid in first said branch stream. For a consideration of what we believe to be novel and our invention reference is made to theiollowing description and the claims appended thereto in ,con nection with the accompanying drawings in which by way of non-limiting examples Fig. 1 shows an embodiment of a plant for utilizing pulverized coal as fuel.

Fig. .2 represents an alternative embodiment as for utilizing ordinary coal or other solid fuel on a travellinggrate-and control'means' for such plant. Fig. 3 indicates an alternative arrangementto Fig. 1 with means for admixing colder com- 7 Dressed air to the hot airfat the inletsto the air during their passage through the regenerative turbines. I

Referring now to Fig. 1, the illustrated arrangement comprises a compressor l0 having an inlet conduit I torreceiving air from the atmos- 5 phere, conduit II for discharging compressed air. I This air enters surface type heater |3 via'threeway valve l4 and branch conduits l5 and IS. The headers I1 and It or theheating device are connected by tubes for the compressed air and divided by walls I1 and 3', so as to keep the branch streams entering through conduits l5 and I6 separate. From header |8 conduits l9 and 2|! lead the air to the inlets of turbines 2| and 22 respectively. in which said air is expanded and discharged through'conduits 23 and-24, Joining into conduit 25; and thence into the gas channel of heater I! at 26, where the-temperature is-just about equal tothat of the entering air. An ex- I haust conduit 3| allows the gases and air to escape to the atmosphere. Between points 26 and exhaust conduit 3| conduit 21 isdisposed allowing'the withdrawal of the mixture of combustion gas and air. The conduit, in'which fan 28 is interposed, is connected to the combustion chamlll ber III via burner for pulverized coal 29. This combustion chamber.

burner receives coal from valved pipe 32 from a source not shown.

As indicated in the drawing, turbine 22 is mechanically coupled to compressor l0, while turblue 2! is so coupled to a power consuming device which in the example is an electric generator 33. A motor 34 of any kind is provided for starting the plant.

The plant operates as follows:

At maximum load valve I4 is adjusted to allow unrestricted air flow to conduits l5 and it which are dimensioned to allow passage for .the air quantities required by the turbines 2| and 22 respectively. The air-gas mixture entering, combustion chamber 30 via conduit 21 and fan 28, serves as combustion supporting medium for the pulverized coal fed through pipe 32. The resulting hot gases of combustion are led through the heater, as indicated by the dotted line, substantially in counterflow to the compressed air passing through the tubes of the heater, being thereafter discharged to the atmosphere through conduit 3|.

Only a portion of the air-gasmixture from the heater is used ,for combustion; the remainder passes throughthe rest of the heater which serves simultaneously as recuperatorfor the heat in the air discharged from the turbines.

The point in the gas stream to which conduit 21 is connectedis s selected,that the temperature of the air-gas mixture is suitable for the burner.

At other loads valve I4 is adjusted to vary the air quantities flowing to the respective turbines. The rate of fuel supply is adjusted by valve in pipe 32, the rate of admittance of, the combustion supporting medium to the combustion chamber by adjusting the speed of fan 28. The temperature of either branch stream of compressed air leaving the heating means may be controlled, as known in the art, by admitting unheated compressed air branched ofi in front of the heating means. Fig. .3shows such an arrangement suitable for embodiment in plant as perzFig. 1. A conduit 50 is branched off from the compressor discharge conduit l2 and connected via control valves 5! and 52 to both conduits l9 and respectively. If the air temperature'in either of these latter conduits exceeds a desirable value, valves 5i and/ or 52 are operated to admix air from conduit l2..

Fig. 2 shows an embodiment suitedfor burning coal on a travelling grate with forced draft. The operation is generally similar to that of arrangement as per Fig. l; the main diiierence lies in the design of the heater and the control of the plant.

Instead of thecoal burner, grate 29' is disposed in combustion chamber 30, fromwhiph the combustion gases are led through the heater in two separate parallel streams as indicated by dotted lines, and discharged also separately through separate conduits3l and3l. The combustion supporting medium is withdrawn from conduit 3| via conduit 28', fan -28" and damper 28" to the Air from the turbines is led into the two separate gas streams by two separate conduits 2 5 and at points where the gas temperatures are just about equal to the temperatures or the said air coming from the turbines. a v

For purposes of loadcontrol, valve [4 is provided with control lever which is connected by lever and rods 35 to damper 31 disposed within con-, duit 3|. The fulcrum of lever 38 is supported by bellows 38' of a vapor-pressure type thermostat 38 disposed in the inlet conduit to turbine 2i and connected to it by pipe 39. Furthermore the grate is equipped with a slide 40 for adjusting the thickness of the coal layer on the grate. This slide is connected by lever H to rod 42 and to the bellows 43 of a thermostat 44 disposed in the inlet conduit to turbine 22 and connected to it by pipe 45. Rod 42 is also connected to the beforementioned hand lever 35 by rods and bell cranks 46 as indicated.

The control operates as follows:

If the plant operates at partial load, in which case the air flow to conduit I5 is restricted by valve l4, and a higher load is desired, lever 34 is moved anticlockwise, thus admitting more air toturbine 2|. To meet the higher heating requirements in the upper tubes of the heater, damper 31 is opened more, being operated by rods and lever 36. Opening of damper 31 reduces the flow resistance in conduit 3! and more gases from the combustion chamber are available for heating the upper tubes. The necessary increase in fuel supply for the higher load is initiated also by hand lever 35 acting on rods and cranks 46, causing rod 42 to lift lever 4i round the supporting point of the bellows 43 as fixed point, thus raising slide. 40 for an increased coal supply to the grate, and raising damper 28 for admitting more combustion supporting medium to the cornbustion chamber.

The purpose or thermostat 38 and-bellows 38 is to prevent the temperature at the inlet to turbin 2| from rising inadmissibly. In such case the bellows 38' expand, moving the left hand end conduit 20, should rise too high, bellows 43 expand and move lever 4| round point 4|" as fixed point, so that slide valve 40 and damper 28" tend to close somewhat, with the result that less coal is burned and the temperature in conduit 20 restored to normal.

It is evident that by avoiding exposure of all how control means to high temperatures, greater reliability in operation is attained, quite apart of the lower costs for these parts.

.It is immaterial for this invention what types turbines or compressors are used, whether or not intercooling or the air before or during compression, and reheating during expansion are employed. v

While preferred illustrative embodiments of the invention have been shown and described, it is to be understood that various modifications in the details of construction and mode of operation may be resorted to without departing from the spirit of the invention within the definition of the appended claims.

What we claim is:

1. In combustion turbine power plants including a compressor driving turbine and a useful power turbine, said two turbines being mechanically independent of each other and arranged in parallel with respect to the flow of the working fluid, the combination of fuel burning means for creating a heating gas stream, conduit means for said heating gas stream, heating surfaces arranged to transfer the heat of said gas stream onto the compressed working fluid, conduit means for bifurcating the stream of the compressed working fluid in front of its inlet to said heating means, conduit means for leading two separate branch streams of the compressed working fluid past said heating surfaces into said two turbines, means for controlling the flow resistance of at least one of said branch conduits disposed in front of its inlet to said heating means, and conduit means connecting the outlet of at least one of said turbines to a point of said heating gas conduit where the gas temperature is substantially equal to or lower than the temperature of the expanded working fluid prior to its admixture to the gas stream.

2. In combustion turbine power plants according to claim 1, using air as working fluid, conduit means connecting the combustion air inlet of said fuel burning means with said conduit means for heating gas at a point past said heating surfaces.

3. In combustion turbine power plants according to claim 1, using air as working fluid, conduit means connecting the combustion air inlet of said,

fuel burning means with that intermediate point of said conduit means for the heating gas stream where said stream has reached by heat transfer a temperature permissible for said fuel burning means.

4. In combustion turbine power plants including a compressor driving turbine and a useful power turbine, said two turbines being mechanically independent of each other and arranged in parallel with respect to the flow of the working fluid, the combination of fuel burning means for creating a heating gas stream, conduit means for bifurcating said heating as stream, conduit means forming two separate branch streams of said heating gas, heating surfaces arranged to transfer heat of said branch streams onto the compressed working fluid, means for controlling the flow resistance of at least one of said branch conduits disposed past said heating surfaces, means for bifurcating the stream of the compressed working fiuid disposed in front of its inlet to said heating surfaces, conduit means forming two separate branch streams of the compressed working fluid, each being arranged in heat exchange relation to one of said branch streams of the heating gas, and means for controlling the flow resistance of at least one of said branch conduits for the compressed working fluid, said controlling means being disposed in front of the inlet to said heating means.

5. In combustion turbine power plants according to claim 4, conduit means connecting the outlet of each turbine to an intermediate point of that heating gas branch conduit whichis in heat exchange relation to the compressed working fluid branch conduit connected to said same turbine.

6. In combustion turbine power plants according to claim 4, means for joint flow control in two branch conduits disposed in heat exchange relation to each other.

FREDERICK NETTEL. JOHN KREITNER. 

